Rory McIlroy has revealed how he gambled on rivals Phil Mickelson and Rickie Fowler not making an eagle in a frantic finish to the US PGA Championship on Sunday.

With daylight fading fast following a rain delay of almost two hours, Mickelson and Fowler stood aside on the 18th hole to allow the final group of McIlroy and Bernd Wiesberger to tee off.

That ensured they would have the option to finish the hole and is common practice, but what was not so common was McIlroy hitting his approach to the 18th as well before Mickelson and Fowler attempted to catch him with an eagle three on the par five.

"We were cool with hitting the tee shot," Fowler said. "We weren't expecting the approach shots. It changes things a little bit. Obviously, there is no waiting. Phil and I waited on the tee for a good amount of time and had to hit tee shots.

"In a way, they [McIlroy and Wiesberger] never got out of rhythm as far as hitting the golf shots."

Mickelson, who came agonisingly close to holing his pitch, stopped short of criticising the situation in a television interview but was clearly agitated on the green.

"It didn't affect the outcome I think," the left-hander said. "It's not what we normally do but it's not a big deal. It's a courteous thing to let the guys tee off in case they blow the horn. It gave everyone a chance to finish just in the nick of time."

McIlroy was quick to acknowledge the act of sportsmanship after hitting his second shot into a greenside bunker and securing the par which sealed a one-shot win over Mickelson and a second major title in four weeks.

"They could have just left us on the tee box there and just play normally," McIlroy said. "But they showed a lot of class and a lot of sportsmanship doing that. I thanked Rickie and Phil in the scorer's area and reiterated what I said in my speech out there on the 18th green.

"At that point in time, I had a two-shot lead. I saw both their second shots and I saw that they had finished down on the bottom right side of the green. I knew it was tough.

"I know Phil came awfully close to holing that third shot but at the same time, I knew par was probably going to be good enough, and if I had to and try and make birdie with that third shot out of the bunker, I would have been a little more aggressive with it and obviously tried to get it up on the top level and try and make a four.

"But I just sort of weighed up the probability of everything and I was 75, 80 per cent certain that those guys were not going to make eagle. So it made my job a little easier."